错误提示：Fatal error: Call to undefined function mysqli_num_row()

<?phprequire ('inc/config.php');$page_title = '注册-CNode博客';include ('inc/header.php');if ($_SERVER['REQUEST_METHOD'] == 'POST') {	require (MYSQL);	$trimmed = array_map('trim', $_POST);	$errors = array();	if ($_POST['code'] != $_SESSION['code']) {		$errors[] = '验证码不正确!';	}	if(empty($trimmed['username'])) {		$errors[] = '用户名不能为空';	} else {		if (preg_match ('/^[A-Z \'.-]{5,20}$/i', $trimmed['username'])) {			$un = mysqli_real_escape_string ($conn, $trimmed['username']);		} else {			$errors[] = '您的用户名格式不对';		}	}		if(empty($trimmed['email'])) {		$errors[] = '电子邮件地址不能为空';	} else {		if (filter_var($trimmed['email'], FILTER_VALIDATE_EMAIL)) {			$e = mysqli_real_escape_string ($conn, $trimmed['email']);		} else {			$errors[] = '您的电子邮件地址格式不对';		}	}		if(!empty($trimmed['password'])) {				if (preg_match ('/^\w{4,20}$/', $trimmed['password']) ) {			if ($trimmed['password'] == $trimmed['notpassword']) {				$p = mysqli_real_escape_string ($conn, $trimmed['password']);			} else {				$errors[] = '登录密码和确认密码不一致';			}		} else {			$errors[] = '请输入有效的登录密码';		}			} else {		$errors[] = '登录密码不能为空';	}		if(empty($trimmed['notpassword'])) {		$errors[] = '确认密码不能为空';	}		if (empty($errors)) {		// 确定电子邮件是否被使用		$q = "SELECT user_id FROM users WHERE email='$e'";		$r = mysqli_query ($conn, $q) or trigger_error("Query: $q\n<br />MySQL Error: " . mysqli_error($conn));		if (mysqli_num_row($r) == 0) { // 如果查询验证电子邮件地址未被使用，则注册用户			$a = md5(uniqid(rand(), true)); // 创建一个激活码（创建一个长度正好为32个字符的字符串）			$q = "INSERT INTO users (username, email, password, active, registration_date) VALUES ('$un', '$e', SHA1('$p'), '$a', NOW() )";			$r = mysqli_query ($conn, $q) or trigger_error("Query: $q\n<br />MySQL Error: " . mysqli_error($conn));				if (mysqli_affected_rows($conn) == 1) {				$body = "感谢您的注册，激活您的帐户，请点击这里：\n\n";				$body .= BASE_URL . 'activate.php?x=' . urlencode($e) . "&y=$a";				mail($trimmed['email'], '确认注册', $body, 'From: 414412984@qq.com');				echo '<h3>感谢您的注册！一封确认邮件已经发送到您的邮箱。请在该电子邮件中单击链接，以激活您的帐户。</h3>';				exit();		 	} else { 				echo '<p class="error">用户注册失败，为此我们表示抱歉，请在注册一次</p>';			}				} else { // 查询验证出来的电子邮件地址已经被注册			echo '<p class="error">电子邮件地址已经被注册</p>';		}	} else {		foreach ($errors as $msg) { // Print each error.			echo " - $msg<br />\n";		}	}	mysqli_close($conn);}?><div class="wrap login">	<div class="path"><a href="#">主页</a> > 注册</div>	<div class="info">    <form method="post" name="register" action="">		<p>		  <label for="username">用户名：</label><input type="text" name="username" id="username" class="text" value="<?php if (isset($trimmed['username'])) echo $trimmed['username']; ?>" />		  <span>限5~20个字符，可用中文、英文、数字及“_”、“-”组成</span>		</p>        <p>          <label for="email">电子邮件：</label><input type="text" name="email" id="email" class="text" value="<?php if (isset($trimmed['email'])) echo $trimmed['email']; ?>" />          <span>请填写您的常用邮箱，它是您激活帐号和找回密码的凭证!</span>        </p>        		<p>		  <label for="password">登录密码：</label><input type="password" name="password" id="password" class="text" value="<?php if (isset($trimmed['password'])) echo $trimmed['password']; ?>" />		  <span>密码由4-20位字母、数字组成</span>		</p>		<p>          <label for="notpassword">确认密码：</label><input type="password" name="notpassword" id="notpassword" class="text" value="<?php if (isset($trimmed['notpassword'])) echo $trimmed['notpassword']; ?>" />          <span>请再次输入密码</span>        </p>				<p>		  <label for="yzm">验证码：</label><input type="text" name="code" id="yzm" class="text1" />		  <img  src="code.php" id="code" / alt="错误提示：Fatal error: Call to undefined function mysqli_num_row()" >          <span>看不清，请重新点击验证码(注意大小写)</span>		</p>		<div class="submit">		   <input type="submit" name="submit" class="btn-1" value="立即注册" />		</div>	</form>	</div>	</div>	<?phpinclude ('inc/footer.php');?>

print_r(get_extension_funcs('mysqli'));